Consider these different plastic manufacturing processes.
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When it comes to producing end-use parts and products, one material stands out the most – Plastic. There are thousands of polymer options and every one of them has a specific mechanical property. With this material we can make almost everything and there is a variety of plastic manufacturing processes that covers a wide range of different needs in product developing.
But manufacturing options can be very limited, for example geometry and design require significant design for manufacturing (DFM) optimization.
By inflating a heated plastic tube inside a mold we can create a hollow plastic parts. This type of manufacturing process operates at far lower pressure than injection molding. It has a lower tolling cost then injection molding. Blow molding is the most common process for creating plastic bottles, toys, automotive parts etc…
- Small plastic pellets are melted and formed into a hollow tube (parison).
- Parison is clamped into a mold and inflated by pressurized air.
- The part is cooling until it is solid enought to be ejected.
Machinery for this process is relatively cheap as it is less complex. Extrusion molding is almost a continous process, which makes the price of the products very low. Products that are most commonly made are pipes, straws, hoses and window frames.
Plastic is heated and pushed through a heated chamber by a screw, then forced through a die that creates a final shape of the part. The extruded plastic is cooled then spooled or cut into desired length.
Molds for this process are higly complex and due to the high temperature and pressure involved these molds are made from metals like hardened steel and aluminium (which is less expensive). DFM helps Injection Molding process to keep tooling managable. Lead time for completing new molds is aproximatly one month.
When it comes to process, the mold is closed by hydraulic press, then the small plastic pellets are melted and extruded by a screw. The molten plastic is then injected into a mold. The part is then cooled into a mold until is solid enough to be ejected, and at the end sprues, runners and any flash is removed from a part.
4. Vacuum Forming
Vacuum formed products are common: product packaging, shower trays, car door liners, boat hulls…
Tooling cost for this process is low compared to other molding techniques. Molds are made from wood, plasters and 3D printed resin, but for high production volumes metal tooling can be used as well. In this process plastic is streched over the mold while vacuum is activated to suck all the air out between the plastic and the mold
Rotation molding is also called rotomolding, and it is used to produce mainly large hollow objects. Rotomolding creates parts with nearly uniform wall thickness. The cost of the parts are very low relative to the size of the part. It is ideal for short-run production or as an alternative to blow molding for lower volumes.
For this process molds are made form latex rubber or room temperature vulcanized silicone rubber, but only a limited number can be produced (between 25 to 100). This molds can reproduce even a smallest details. Polymer casting is typicaly used for prototyping and short production.
7. CNC machining
CNC machining is unique process where material is removed by a spinning tool and a fixed part. This is ideal for low volume plastic part application that requires geometrics that are difficult to mold. This process can produce high-quality plastic components with short lead time. Cost per part increases with part complexity.
8. 3D Printing
3D printing process is generaly slower and for some printers it takes days to print complex parts. As this process keeps improving cost per part continues to drop. This type of production requires no tooling and minimal setup time for a new desing. It can create three-dimensional parts directly from CAD models by building material layer by layer until is complete.